This invention relates to an apparatus for locking a shift lever associated with an automobile automatic transmisson in the parking range.
As is well known in the art, in automobiles having an automatic transmission mounted, the engine and the transmission gear are connected through a fluid coupling. The power of the engine is transmitted to the wheels except when the transmission gear is kept in the parking or neutral state. In general, a provision is made such that the engine can be started only when a shift lever for drive control is set in the parking or neutral range. It is also a conventional practice that the brake pedal must be stepped down to accomplish a braked state before the shift lever can be moved from the parking or neutral range to any driving range such as the drive range.
Such a locking apparatus was proposed by the same assignee as the present invention in Japanese Utility Model Application No. 62-119707. The locking apparatus is briefly described. The locking apparatus includes a detent pin and a ratchet plate having a plurality of engagement portions for engaging the detent pin. In association with those engagement portions which the detent pin engages when the shift lever is set to the parking and neutral ranges, a lock piece is provided for preventing the detent pin from disengaging from the engagement portion. A slide plate is provided in combination with the lock piece for moving the lock piece between locking and unlocking positions. An electromagnet is disposed for driving the slide plate. When the requirement is met, for example, if the brake pedal is stepped down or additionally, the engine is rotating at a revolution number below a certain value, the electromagnet is actuated to move the slide plate and hence, the lock piece to the unlocking position, allowing the shift lever to be changed from the parking or neutral range to any desired driving range. In addition, a part of the surface of the lock piece to be in contact with the detent pin is so slanted that an increased push-buttin manipulation can positively unlock the lock piece independent of the electromagnet, also allowing free change of the shift lever.
Since the locking apparatus of the above construction uses the electromagnet as an actuator, it is suitably combined with an automatic transmission of the electronic control type wherein control is carried out by detecting various parameters followed by electric processing. The locking apparatus, however, is not suitable for an automatic transmission of the hydraulic control type because several sensors must be additionally incorporated, resulting in a further complicated structure. This adds to the disadvantage that the locking apparatus is rather complicated as such because it is designed to lock the shift lever in the neutral range as well as the parking range.
There is a need for a shift lever locking apparatus which is of a simple construction and advantageously applicable to not only automatic transmissions of the electronic control type, but also automatic transmissions of the hydraulic control type.